Egypt is searching for 120 wanted militants and believes around 1,600 extremists are hiding out in the Sinai, where militants have attacked soldiers and police, the official news agency MENA reported on Wednesday.
The military sent in tanks and soldiers into the lawless peninsula which neighbours Israel and Gaza after gunmen killed 16 soldiers in an attack on an army outpost on August 5.
"There are 120 people wanted, including groups that attacked police stations and killed a number of policemen," MENA quoted a security official as saying.
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Most of them follow "takfiri" ideology, he said, a disparaging term for extremists who excommunicate other Muslims who do not share their beliefs.
"Their numbers are close to 1,600 people, from different provinces and some from other countries," he said.
Gunmen wounded three policemen last weekend when they fired a rocket-propelled grenade on a police convoy, several days after security forces killed six militants in a raid on a north Sinai village.
The government has long struggled with militancy and smuggling in the region but unrest has worsened since an uprising overthrew president Hosni Mubarak in February 2011, prompting the collapse of his discredited police force.